File extensions – definition and basic information


File extensions are the integral parts of the files that are on each computer. Often, when working on a computer, we encounter a wide range of files, such as docx, ppt, part, mp3 or rmvb. We realize that they are there – but we often do not know what they are for on our computer.

File extension, also known as the filename extension is a suffix added to the name of a computer file, usually consisting of a number of characters placed after the last dot in the filename, which gives us information about its coding. In other words a file extension is a file format. It allows the operating system (e.g. Windows) to recognize what program it should try to open the file.

In the table below you will find a random selection of popular file extensions.


File extension The full name of the file Category

AIF file extension

Audio Interchange File Format

Audio Files

DOC file extension

Microsoft Word Document

Text Files

EPUB file extension

Open eBook File

eBook Files

FLA file extension

Adobe Flash Animation

Developer Files

FON file extension

Generic Font File

Font Files

INDD file extension

Adobe InDesign Document

Layout Files

M4V file extension

iTunes Video File

Video Files

OBJ file extension

Wavefront 3D Object File

3D Image Files

OTF file extension

OpenType Font

Font Files

ROM file extension

N64 Game ROM File

Game Files

SITX file extension

StuffIt X Archive

Compressed Files

TMP file extension

Temporary File

Backup Files

TOAST file extension

Toast Disc Image

Disk Image Files

XLSX file extension

Microsoft Excel Open XML Spreadsheet

Spreadsheet Files

ZIP file extension

Zipped File

Compressed Files